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Silence is Golden, But Not During An MRI

By DuPage Medical Group Radiology

You’ve always heard that silence is golden, but did you realize that an MRI machine needs to make a lot of noise in order to produce those clear images? Don’t worry, in this case, noise is a good thing and it’s caused by a giant magnet.

MRI machines produce images of the body by causing shifts in a very strong magnetic field that is created by running an electrical current through a coiled wire, or electromagnet, and measuring how your body tissues react.

Within the MRI scanner there are coils of metal wire called gradient coils. When electricity is passed through these gradient coils, a magnetic field is created. As the magnetic current is switched on, the force on the coil goes from zero to huge in just milliseconds, causing the coil to expand slightly, which makes a loud "click" noise.

When the MRI machine is making an image, the electrical current is switched on and off rapidly causing predictable changes in the magnetic field and certain body tissues that can be measured and transformed into images.

The result is a rapid-fire knocking noise, which is amplified by the tunnel-shaped space where the patient lies.

But, why is the MRI machine so loud?

Stronger MRI magnets result in stronger vibrations and the higher the field strength of the MRI scanner, the louder the banging noises.

MRI field strength is measured in Tesla (T).In a three-tesla (3T) system, which has only recently become more commonplace, the sounds may be as loud as 125 decibels which is equivalent to a rock concert or a balloon popping near your ear. 


Topics and Subtopics: Diagnostic Testing & Radiology

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